Hydraulic propeller pitch change mechanism



July 29, 1952 E. K. BENEDEK 2,604,951

HYDRAULIC PROPELLER PITCH CHANGE MECHANISM Original Filed May 24, 1941 '7 Sheets-Sheet 1 IN] "EN TOR. ELEK BENEDEK'.

um! L I JTTORXEYS July 29, 1952 E. K. BENEDEK HYDRAULIC PROPELLER PITCH CHANGE MECHANISM Original Filed May 24, 1941 7 Sheets-Sheet 2 ELEK. K. BENEDE K- fly July 29, 1952 E. K. BENEDEK 2,604,951

HYDRAULIC PROPELLER PITCH CHANGE MECHANISM Original Filed May 24, 1941 7 Shgaets-Sheet 3 I l I l l l [NI/[5N TOR. v ELEK K. BENEDE K- July 29, 1952 2,604,951

E. K. BENEDEK HYDRAULIC PROPELLER PITCH CHANGE MECHANISM 7 Sheets-Sheet 4 Original Filed May 24, 1941 w s @R k -w v *3 J J J Q HH' R Q s Q) J J J Q LE! 7C3? ll] Z I: Z r-l 9 P- H 1:1 8 U] Q I H H [I E: P:

. I I! I INVILN'I'OR. Z W ELEK K.BENEDEK- {Wm A'I'TURNEYS July 29, 1952 E. K. BENEDEK 2,604,951

HYDRAULIC PROPELLER PITCH CHANGE MECHANISM Original Filed May 24, 1941 7 Sheets-Sheetfi INVEN TOR.

5 ELEK ILBENEDE K- BY 6; M i jr romvgi July 29, 1952 E. K. BENEDEK HYDRAULIC PROPELLER PITCH CHANGE MECHANISM '7 Sheets-Sheet 6 Original Filed May 24, 1941 INVENTOR. ELEK a K .BENEDEK BY 7 ATTORNEYS July 29, 1952 E. K. BENEDEK HYDRAULIC PROPELLER PITCH CHANGE MECHANISM 7 Sheets-Sheet '7 Original Filed May 24, 1941 K A m.% TE 1 f NN K mm 6 a J r 1K T 3 1 L .E 5 TN d a x w xwmuifiw n mx kw 4; ATTORNEYS Patented July 29, 1952 OFFICE HYDRAULIC PROPELLER PITCH CHANGE MECHANISM Elek K. Benedek, Chicago, Ill. Original application May 24,. 1941, Serial No.

395,080. Divided and :this application August. 13, 1945, Serial .No. 610,536

lli'Claims. l.

Thisapplication is a division of the copending application of Elek K." Benedek, Serial No. 395,080, filed May 24, 1941, which became U; S. Patent No. 2,382,389, issued-August 14, 1945.

This invention relates. to. feathering variable pitch propellers, and particularly to a hydraulic mechanism for controlling the output of the engine by varying the pitch of airplane propeller blades.

Variable pitchpropellers with limited means for angle control have been provided heretofore for use in connection withairplanes.

Originally the pitch .was changedonly between twohmits, these limits being very little and. of a maximum .of to. Thedemands of the industry, now, require that therangeof pitch adjustment be. controlled steadily and .positively and' that .fe'atheringf of. .they propeller be made possible. This isparticularly truein connection. with the growing. tendency toward the use of power descents inairplanes.

It" is one. of the objects. of. the present invention. to provide. a propeller and pitch control mechanism therefor. bywhich the propeller. can bemade tofunction asaconstant speed propeller butwithan increased ..range.of blade pitch ad'- justment..-

Anotherobjectisto provide a propeller and. controlmechanismlby. which... the. pitch of the propeller bladescanbechangedor adjusted in emergencies to. a. more. nearly completely feathered? position, that. is, .aposition in. which their, chordis approximately parallel. .to....the line. oi. fiighh. so.. that the, propeller. blades.v act as brakesfor reducing .the engine. rotationr.

Another object is to provide for effecting. this operation in. relatively few seconds. so. that the engine may. be-stopped promptly. in. case of any engine failureandthe .drag of the .dead. propeller on the. airplane. can be greatly reduced.

Therpresent invention is. characterized in that it i's-..more..simple.than thestructures heretofore providedfor.the;same. purpose, andlprovides. a larger range of pitch control than unreliable hydraulicelements-such as sleeves, valves, and low pressure elementsheretoiore.used, thereby insuring greater. reliability, and; constant maximum engine horsepowerat constant engine speed.

The principalobjects of the present invention are to provide a hydraulic mechanism forv the purposes described, by, which unlimited. pitch range and quick feathering can be obtained, for example, when one of the engines must be stopped, due tov engine. troubles; by which a simple'andleifective oil circuit is providedbetween' actuatingand governing1elements; positive, cone. tinuous, and instantaneous response of" pitch of the propeller blades and for maintainingthem in the desired position of power and loadiequilibirium; and the propeller blades may' bei com.- pletely reversed and pitched to any desiredangle in either direction froma normal or neutral position.

Other objects and advantages will becomeiap -i parent from the following specification. wherein reference is made to the drawings. in which:.

Figure 1 is a diagrammatic illustration of a" preferred embodiment of the present. inventionemploying a reversible fluid pressure circuit in: cluding a pump, a hydro-motor, and means to; control the circuit in response to engine speed? change, and with the motor mechanically, drivingly connected to the blades of the propeller;

Figures 2 and 3 are diagrammatic. frontand side elevations, respectively, of the propeller and; motor illustrated in Figurel, the. pump .being; shown diagrammatically in connection there.- with for clearness in illustration; 1,

Figure 4 is a longitudinal sectional view of the propeller hub and motor assembly and is..tal-:'en.. on a plane indicated by the. line 4.-4 inFi'gureLf Figure 5. is a sectional view takenpn' aplane indicatedby theline 5'5..in Figure 4; j I

Figure 6 is a cross-sectional'view throughithe variable delivery, pump usedin connection with; the present invention and with-a hydraulic servo-e motor used in connection therewith;

Figure 6a is an axial sectionalview of*a*strok,e* adjusting means which maybe-used at the 'right hand side of the pump illustratedin'Figure(i for quick feathering of the propeller;

Figure 7 is an axialsectional view through the propeller drive shaft,.illustrating the oil transefer ring and the manner. in which the. fluidpres: sure is supplied to the hydraulic motor,,theshaft? beingshown in elevationfor clearnessinillustration;

Figure 8'is a sectional view taken one-plane indicated by the line 8'-8"in Figure-7, the:hy.,- draulic circuit. being diagrammaticallyillustrated in connection-therewith;

Figure 9'is a'sectional viewof the propellerhubt showing a planetary speed reducinga gear;- connection between the hydro-motor andlthe proa peller blades and-is a modification:ofitheustruce ture illustrated in Figures 1 to 8;

Figures 10 and 11 are-sectional views taken: on;

planes indicated by the lines Iii-49 and H-i l, respectively, in Figure 9;

Figure 12 is a sectional view taken on the plane indicated by the line l2l2 in Figure 11;

Figure 13 is a graphical representation of the effect of slip in a reversible, variable stroke, high pressure pump;

Figure 14 is a modified circuit employing auxiliary power means for reducing hydraulic backlash; and

Figure 15 is a diagrammatic illustration of a circuit similar to Figure 1, but employing a non reversible pump and constant pressure control with valve means for reversing the flow of the pump with respect to the motor.

Referring first to Figures 1 to 12, inclusive, the invention is embodied in an apparatus wherein the pitch of the propeller blades is changed and set by asingle hydro-motor which is coaxial with thehub or rotational axis of the propeller and usually also with the engine crank shaft. The hydraulic elements may comprise a motor l which can be reversed by reversal of the delivery of the pump so that the motor shaft may swing through an angle a. in either direction from a neutral or normal operating position, as indicated at n in Figure 1. Reversal of the motor may be effected also by suitable valves and a one-way pump, as described hereinafter.

The motor is connected to a variable delivery pump 2 in a circuit comprising pipes 3 and Q leading from opposite sides of the pump to opposite sides of the motor. The opposite sides of the pump circuit are connected to a sump by pipes 5 and 5, respectively, these pipes being provided with pressure check valves '1 and 5. Oil pressure fluid is supplied to the servo-motor 9 through a suitable pipe Illa from the gear pump in of'the engine to actuate the servo-motor which is operative to vary or reverse the pump stroke while the pump continues to be driven in the same direction. The pilot valve of the servo-motor, in turn, is connected by a suitable rod I! to a hand-operated rock lever 12 so that the stroke of the pump may be adjusted or reversed by hand. The rod ll may be connected also to a lever 13 operated by a governor 14 which, in turn, is driven through appropriate means, such as flexible shaft and gears 15, from the engine of the airplane or vehicle. Thus independent hand and governor control are obtained. The pump'2 is continuously driven from the engine of the airplane or vehicle. Consequently, its delivery may be under the control of the governors I4 at all times and, as a result, the setting of the motor l and the pitch of the propeller blades may be controlled in a direct relation to the speed of the engine or prime mover.

The motor I is mounted ina rigid housing 16 which forms the propeller hub and forwardly from which extends a portion in which the propeller blades I! are mounted. The propeller housing 16 and blades are rotated primarily about the propeller axis by the main drive or crank shaft l8 of the engine, the connection between the pump and the motor being effected by means ofan oil transfer ring I9.

' Referring next to Figures 4 and 5, the housing It of the hydro-motor rotates with the propeller or engine shaft 18, the housing it being fixedly secured thereto by splines 20. The outer end portion of the shaft 18 is constructed in the form of a valve pintle 2|, but this pintle may be made separate and attached to the shaft. The pintle 2] has sets of reversible ports 22 and 23,

connected by internal ducts, as illustrated, with reversible ports 24 and 25, respectively, in the shaft it. Mounted on the pintle 2! for rotation relative thereto is a rotatable barrel 25 having a plurality of radial cylinders 21, each cylinder havinga port arranged for successive cooperation with the ports 22 and 23 as the barrel rotates relative to the pintle. Mounted in the cylinders are radial pistons 28, each of which has a head portion 29 guided in suitable guideways 3G, in a a radial flange 31 on the barrel. Each crosshead 29 carries a cross pin 32 which is rotatable in the cross-head 29 on anti-friction needle rollers. The ends of the cross-pins 32 project beyond the heads 29 and engage a reactance means with which they cooperate for effecting rotation of the barrel when fluid pressure is introduced into the cylinders in the proper valving relation. In the form illustrated, an elliptical hydraulically balanced reactance means is provided and comprises outer cam rings 33 and inner cam rings 3d parallel thereto, these rings forming cam tracks with which the ends of the cross pins 32 are in rolling engagement. Thus the barrel can be caused to rotate relative to the shaft l8. Fixedly secured to the barrel at its outer end and coaxial therewith is a synchronizing bevel gear 35 which cooperates with bevel gears 35 mounted on the inner ends of the hubs of the propeller blades 17. This motor is more fully described in my United States Patent No. 2,111,657, but motors described in my United States Patent No. 2,097,830 or 2,101,731 are equally applicable for this purpose.

The propeller blades (1 have their hubs mounted anti-frictionally in a rigid housing 31 which is rigid with the housing It and rotates therewith. Thus, the blades can, through the medium of the bevel gears, be rotated about the axis of their hubs so as to change the pitch of the blades.

The oil transfer ring I9 is arranged for con necting the pump with the motor through the ports 2% and 25, as heretofore described. Thus, by admitting fluid from the pump to the motor. the barrel 26 can be rotated relatively to the propeller shaft or crank shaft l8 and change the setting of the propeller blades and hold the blades in the condition set by controlling the delivery of the pump as hereinafter will be more specifically described. For example, the pressure and delivery of the pump can be increased. to move the blades to a predetermined setting and then adjusted so as to supply only slip fluid for maintaining the blades in the set condition. As heretofore explained, this may be accomplished automatically.

The connection between the pump and the motor is better illustrated in Figure 8, which shows the intermediate oil-transfer ring 9 to valve the discharge of the pump into the motor.

Referring next to Figures 6 and 6d, a preferred embodiment of the pump for use in connection with the hydraulic mechanism is illustrated and is the pump more fully described in my United States Patent No. 1,876,833. Other designs such as shown in United States Patents Nos. 2,111,657

or 2,097,830 are equally applicable for this use.

The illustrative pump comprises a valve pintle 40 having reversible Valving ports 4i and ducts '12, the ports 4! being pressure or suction ports, depending upon the setting of the shifter ring of the pump. Mounted for rotation about and fitting the pintle is a rotatable barrel 43 having radial cylinders 44 and valve ports 45 arranged for successive cooperation with the ports 4! as the barrel rotates. Mounted in the cylinders are radialtreciprocablel pistons: :pref erablyr having .-.T--- headsz litiwhichiengage anrotarm-reactancevflkrorsreciproeatingithee pistons :consequentaupon 0178:" I ti'oniofitthecbarrel: when the: reactance {is a n eccentricirelation:to'zthepiston.-. Irr..the -:-form:;ile- 5;; lustnated; theaeactance comprises rings=suDJ2ort-- ingsthrustiplatesifi ilz-Whichtbear: againstxthe outerisurface- .of the: T:-heads :4 B: respectively; and form wit-ht; surfacess fi I of r the-:- rings-rchordal 58101382 for: slidably accommodating therT-heads; Thencetary reactancegis. carriedjrrraistator fl which :is supported; .assindicatdrat 153 withinia'zcasings-fl ofzthemump: The-=reactancecan:beeadjusted in a= straightrlinevthrough :the median: P181116? of zthe bridges whichiarezbetween the-pintle valve ports-,-:. from aZ-POSitiOILOf eccentricityto one =side o-frthe: pintle axis to azpositio-nzofxeccentricity at the-op. positejsitlee Whemthe=reactance-isaset to,cne:side;- ofrtlre -pi'ntle axis, .rotationsofithevpunrp barrel 433causessone 10f i the: ports: 41 to. become-.apres s'urezport eand theqotherporta41-:tor-'becomeea $110:- 1 tiorr port}. Shifting the reactancednrtheropposite direction from: then center position I will reverse: W thezpump discharge: and. flow through :the ports r 4 h. E'orshifting jthe reactanoer the engine driver-1;.- 5; governor: I this interconnectedvwiththe hydraulic. servo motort 9;. as: described with: reference? to.- Eigureal.

Thezservoemotori9 iszarranged'so-that-itspower: cylinderdia isrmoyed byfiuid-pressure inal direetiomopposite ztogthe: direction-of movement of ethe pilotcp'liinger: 9b: This: cooperationofithe pilotandlpoweitpl'ungersr is desirable-:forrfeatheringe as appears: more: fully :hereina-fter;

Reierringznext' to; Eigurefia; thesservormotor may; be 'supplementedzwith; a cylinder 7 1 anda pistomSH-r OIIGQSidfisO-f: thepistonbeing corn-rested bysazducttfitandra pipe line-.lifi as ill-ustrateddn Ei'gureeiir to:.the .pressu-rezside 0f; the main pump. Miamshown inl i'gri:v Th'llSr:thBStT0kG can.-.becontrollediby-the-rcontrol of.pressurerintroducedl from; the; piston; 61;- by; means: 01 thevalve- 64 Itrwill.;be:seen from-Fig. 8; thatcracking valve.

64 for the purpose of a sudden or-a'emergencyi shift oi pistonendzpistomrod 161'; shown also-in 45 Fig: .65 at the; righthand; sidez of: shifter-r ring: 5 2, and'zin .zF-ig. 6min cylinder-(iii;- W'fll'iby I102 means change the: chief. caracteris-tics: of the-operating oil "circuitlbetweenipump 5d andritswconnectedlhy draulic motonasshownffiirther iniIig .41. In'Eigw: 4 the-R? V; D. pump-rand;the;reversiblezvariable. speed mctor: M as at: l 6 i &IBZ.ShOWIL'JiH=* a; closed. hydraulic; circuit; wherein: to; every'fi-xedstroke. position of the pump belongss-only one fixedspeeck operation oi tlie hydro-motor, and Vice versa;-.to.- each speed position. of the. motor belongsonly- 0ne=stroke- :positionxofrtthe: pump: In; thevclosed circuit it: is alsonimperative, that in .eaeh neutral (zero-delivery) positionc.o f ithe.-pump (R,-=1 V.- D-. th'e motor M 'is locked: up 1 in ,fixedz interlocked, braked 'position-by'- the hydraulic fiiiidionly ofthe? closed hydrauliczcircuitx. Suchrinterlockediclosed position 0)? the hydro-motor M; ,or- IE3, and .theoperated-blades l i -fires; in. Figs. 4,: .is. highly, desirable, particularly for: thes.featheringggoperaw 6 5 tion of thebladess. Both forzsafety a-nd'thechanacter of 'emergency operation:in;1a-. feathering; it i ny t t tgzshifti thesshi-fter; ring; 52 quickly and positively-in View ofrtheicontrolling lack of the governor l4;- by:th'e mainpressure into; the desired feathering position of thee; bladess: But by -Operating the-servo-motorc9iviarthezmain pressure-,-- by momentarily-directing pressure-fluid through valve 6 3 'and' line' 63 ,into cylinder 60 ill:- stead'bi by' usingaauxiliary'afluidz ofsgea-n pump;

lfl sof-i-Figg-i {L -the:safety-andprecision of thee-op erationt of: then-main: hydraulic: closed? circuit:- is,

increased :in :case .ofi. an emergency; withoutims pairing gany basic: feature-bf I it; because after the-= feathering, valve :64-i will be iclosed again, serveemotori-9eand gear pump I05 Willgtakeroverrthe pitch controllingoperationfof-the blades. I '|-I 1. In an hydraulic closed-:circuit, thepump and: motor are never independent frdm oneanother. Theygrnutually cooperate for safety andefiic-iency via:the practically incompressible=hydrauliciiuidz medium:

Referring next toFigures 9.-to;-12, a-.mechani-.-- cal; reductionigearings is? used between'the. shaft ofitheahydro-rmotor andthe propeller. bladesior. increasing the. turningmoment of the motor: In this; modification,- thehydro-motor shaft 10- carries. 3;;51'113 '11 .gea-rj. H which is, d-rivingly.--con.--v nectedto: gears 'l2, which are-connectedio adisc. Ii-hayinga-shaft 'l l'onwhich is-mounted abevel gean 15; Therbevel gear. I5 is. drivinglyconnectedto the-bevel gears 1610f therespectivepro peller blades so that reduction is; provided bee tweenthel-shaft lll of. the. main-bevel gear I5. In connection with. Figure 11, .thepropeller blade hub," immounted on elongated cagelessaneedle rollers -'l8--and thrustrbearings 19,- for withstandingttransverse and centrifugal forces.

Referring, nextto Figure 13, there is effective.

; slip. in "the. reversible, variable. stroke, high pressurepumpvwhich causes a so-called hydraulic back-lash during the slip stroke So in either direction of. shift, due to the fact that the slip volume D0 causes-only an internal flow which isa loss .and not eiiective as. external output... Inorder to:eliminate this hydraulic backelash. from the 1 pump and .motor; circuit, an .auxiliary, source of power may beintroducedcn each side ofthe circuit, as illustrated.,.on Figurel, where..- in atone-way pumpequippedwith. an automatic. pressure control C.-will..maintain.. a..constant.,pres.- sure on each side of the neutral. during; reversal. of..the main. pump. stroke. The auxiliarypumps. Paareso dimensionedthat they maysupply the. intake fluid; of the: mainv pump, and. thus the. pressure ,check valves and suction valves. may be eliminated.

Referring next. to Figure 15,,there. isillustrated, a reversible circuitsimilarto Figure. 1,.

except that: instead.- of a reversible. pump on servo-motor; a 1 one-way pump: equipped. vvitha constant.pressure;.control C. is used withia four:- waywalyerv, for-reversing thefiow. of. themoton. The four-way valve V'may, becdirectly or.indi-.. rectlyi connectedto .or. actuated by. agovernon In,operation, the control spring ,ofrthe control .C. isadjusted so that it. counteracts the-torsionalmomentiofrthe propellerblades,.in a setposition. and. automatically holds the. equilibrium with this --.t0rsional moment when. the .valve is open. in. a givencd-irection. Whenthe valve V isshifted to reverse the direction-of. flowfor effecting reversaL- of. the.- motor,. the: pump, automatically holds.='the.-.blades in:.that positionselected. The. pitchis changed by'pressure; as-soon astha-ene gine speed changes; the pressureincreasesor de creases: and: permitsvthechanges of the stroke of the pump. by the: automatic pressure-control to vary; the chord angle of. thez bladeeacc'ording toxthe new equilibrium. Quicki featherin canbe: obtained. by increasing the. pressure-in this: directionto -.overcome all. moments acting: .on the blades: as contrary toa normal -.cy cle; where the counter-moment of torsion holds; the": propeller: ainst 1 the balancing; pressurerof? thflzPliHlPg: at.

an angle less than 90". For feathering, the chord of the angle of pitch becomes parallel to the direction of flight. Thus, this circuit arrangement takes advantage of the counter-movement of the blades to reduce the pitch angle, and the hydraulic pressure really acts only to increase the pitch angle in one direction only toward the maximum limit of feathering.

I claim:

1. In a propeller mechanism, a hub, an engine connected to said hub for driving the hub, a plurality of radial blades mounted on the hub for concurrent rotation therewith and for pitch varying movements about their respective radial axes; a closed fluid circuit reversible variable speed hydraulic transmission mechanism including a variable stroke pump operatively interposed between said hub and said blades respectively to rotate said blades in a forward and reverse direction and thereby increase or decrease the working pitch of said blades; stroke varying means including an hydraulicdevice connected to said pump to change the'speed and direction of rotation of pitch varying movements, a speed responsive device drivingly connected to said stroke varying means, means drivingly interconnecting the engine and the speed responsive device, and a source of hydraulic pressure independent of said variable speed transmission connected to said hydraulic device, and a substantially constant speed drive connected to said pump.

2. In a propeller mechanism, a hub, an engine connected, to said hub for driving the hub, a plurality of radial blades mounted on the hub for concurrent rotation therewith and for pitch varying movements about their respective radial axes; a closed fluid circuit reversible variable speed hydraulic transmission mechanism including a variable stroke reversible pump and a reversible hydraulic motor operatively interposed between said hub and said blades respectively to rotate said blades in a forward and reverse direction and thereby increase or decrease the working pitch of said blades, stroke reversing means including an hydraulic device connected to said pump to change the speed and direction of rotation of pitch varying movements, a speed responsive device drivingly connected to said stroke reversingmeans, means drivingly interconnecting the engine and the speed responsive device, and a source of hydraulic pressure independent of said variable speed transmission connected to said hydraulic device to operate the same in response to the movement of said speed responsive device, a fluid supply means for said transmission mechanism, conduit means for connecting said reversible pump with said reversible hydraulic motor in a closed fluid circuit, and valve means for connecting each conduit means selectively with said fluid supply means.

3. In a propeller mechanism, a hub for connection to an engine for driving the hub, a plurality of radial blades mounted on the hub for concurrent rotation therewith and for pitch varying movements about their respective radial axes; hydraulic means including a variable delivery ccnstant speed reversible pump and a reversible hydraulic motor, said pump and said motor being interconnected in a reversible closed fluid circuit and operatively interposed between said hub and said blades respectively to bydraulically interlock said pump with said motor in any adjusted pitch position of the blades; stroke controlling'means including an hydraulic device connected to said pump to change the speed and the direction of rotation of said motor and the connected blades respectively, a speed responsive device drivingly connected to said stroke controlling means, means drivingly interconnecting the engine and the speed responsive device, and manually operable means connected to said stroke controlling device for changing the stroke of the pump independently from said speed responsive device.

4. In a propeller mechanism, a hub, an engine including a drive shaft connected to said hub for driving the hub, a plurality of radial blades mounted on the hub for concurrent rotation therewith and for pitch varying movements about their respective radial axes; hydraulic meansincluding a variable delivery constant speed reversible pump and a reversible hydraulic motor, said pump and said motor being operatively interconnected in a reversible closed fluid circuit whereby in any neutral position of the pump the motor and the blades will be hydraulically interlocked in their adjusted position by the pressure of said closed hydraulic circuit; said motor being mounted on said drive shaft and in relative rotation thereto, a housing cone nected to said hub surrounding said motor and carried by said shaft in rigid relation thereto, fluid transfer means hydraulically connected to said pumpsurrounding said shaft in stationary relation thereto, fluid passage means in said shaft interconnecting said pump and said fluid transfer means respectively with said motor in a closed hydraulic circuit, a rotary barrel for said motor, cylinders in the barrel, pistons in the cylinders and means connected to the outer end of the pistons for actuating the pistons radially in and out, and means in said housing to receive and actuate last named means, and means to provide driving connection between the cylinder barrel of the motor and the blades of the hub for efiecting pitch-varying movement of the blades consequent upon rotation of said barrel relative to said shaft.

'5. In a propeller mechanism, a hub, an engine including a drive shaft connected to said hub, a valve pintle formed integrally with said shaft and projecting therefrom, a plurality of radial blades mounted on the hub for concurrent rotation therewith and for pitch varying movements about their respective radial axes; a closed circuit reversible variable speed hydraulic transmission mechanism including a reversible hydraulic motor operatively interposed between said hub and said blades respectively to rotate said blades in a forward and reverse direction and thereby increase or decrease said pitch varying movements, said motor being mounted on said central valve pintle coaxial with the hub and secured thereto to rotate therewith, a cylinder barrel rotatable about said pintle relatively to said hub, housing means carried by and rotatable with said hub and pintle, pistons mounted radially in the cylinder barrel, and connections between the pistons and said housing means, driving connections between said cylinder barrel and said blades for effecting pitch varying movement of the blades upon rotation of said barrel relatively to said pintle, and means for supplying fluid under pressure through said valve pintle to said cylinders.

6. In an hydraulic propeller mechanism including a hub, an engine connected to said hub for driving the hub, a plurality of radial blades mounted on said hub for concurrent rotation therewith and for pitch varying movements about their radial axes; a variable speed reversible hydraulic transmission mechanism including a reversible stroke pump and a reversible stroke motor operatively interposed between said hub and said blades, a fluid supply passage and a fluid return passage respectively connecting said pump and said hydraulic motor in a closed reversible fluid circuit, stroke varying means including an hydraulic device connected to said pump to change the speed and direction of rotation of said motor and of said pitch varying movements respectively, valve means interconnecting said stroke varying means with said supply passage of said pump and motor for shifting the stroke of the pump in response to the opening of said valve means for effecting quick emergency feathering of the blades.

7. In an hydraulic propeller mechanism including a hub, an engine connected to said hub for driving the hub and having a projecting reduced diameter pintle portion, a plurality of radial blades mounted on said hub for concurrent rotation therewith and for pitch varying movements about their radial axes; a variable speed reversible hydraulic transmission mechanism including a pump and a reversible stroke fluid motor operatively interposed between said hub and said blades, a fluid supply passage and a fluid discharge passage respectively connecting said pump with said motor in a closed fluid circuit, said motor including a cylinder barrel rotatable about said pintle relatively to said hub, cylinders in said cylinder barrel, reactance means carried by and rotatable with said hub and pintle, pistons mounted in the cylinders of the barrel, and connections between the pistons and reactance means, driving means fixed to said cylinder barrel and being coaxial with said hub and pintle, mechanical means connecting said driving means with said blades, and fluid transfer means for supplying fluid under pressure through said valve pintle to said cylinders and said motor respectively.

8. In a propeller mechanism including a retatable propeller shaft, a hub mounted on said shaft for rotation therewith, an engine connected to said shaft for driving the hub, a plurality of radial blades mounted on the hub for concurrent rotation therewith and for pitch varying movements about their respective radial axes; a closed fluid circuit reversible variable speed hydraulic transmission mechanism operatively interposed between said hub and said blades respectively, said transmission mechanism including a reversible delivery constant speed pump and a hydraulic motor, a fluid supply passage, a fluid discharge passage connecting respectively the corresponding sides of the pump and the motor, stroke varying means including a stationary shifter ring connected to said pump, a hydraulic device rigidly connected to said shifter ring to change the volume and the direction of fluid supply of the pump and the speed and direction of said motor and the pitch varying movements respectively, a speed responsive device drivingly connected to said stroke varying means, means drivingly interconnecting the engine and the speed responsive device, and hydraulic means other than said pump connected to said hydraulic device for actuating said stroke varying means and the interconnected shifter ring of the pump.

9. In a propeller mechanism, a hub, an engine connected to said hub for driving the hub,

a plurality of radial blades mounted on the hub for concurrent rotation therewith and for pitch varying movements about their respective radial axes; a closed hydraulic circuit reversible hydraulic transmission mechanism operatively interposed between said hub and said blades respectively, said transmission mechanism including a reversible variable delivery pump and a hydraulic motor, speed responsive means driven by the engine, and control means connected to said pump and to said speed responsive means respectively to adjust the strike and therewith the delivery of said pump in response to the variation of the speed of the said engine, said control means including a power cylinder and piston assembly and an auxiliary source of fluid pressure connected to said assembly, a pilot valve for said assembly, a speed responsive device drivingly connected to the pilot valve of said assembly, means drivingly interconnecting the engine and said speed responsive device, and means hydraulically interconnecting said auxiliary source of pressure power with said power piston and cylinder assembly, said power assembly and said pilot valve adjusting the stroke of said pump and the interlocked angular position of said motor and connected blades respectively in response to the shifting of said pilot valve by said speed responsive device.

10. In a propeller mechanism, a hub, an engine connected to said hub for driving the hub, a plurality of radial blades mounted on the hub for concurrent rotation therewith and for pitch varying movements about their respective radial axes; a closed fluid circuit reversible variable speed hydraulic transmission mechanism including a variable delivery radial piston reversible pump and a variable speed radial piston reversible motor and a fluid supply passage'and a fluid discharge passage connecting the pump with the motor, all operatively interposed between said hub and said blades, stroke varying means including a hydraulic device connected to said pump to change the speed and direction of rotation of pitch varying movements, a speed responsive device drivingly connected to said stroke varying means, means drivingly interconnecting the engine and the speed responsive device, a source of hydraulic pressure power independent of said variable speed transmission connected to said hydraulic device, and manually operable means connected to said stroke varying means for feathering said blades.

ELEK K. BENEDEK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 20,551 Rouse Nov. 9, 1937 1,723,617 Hele-shaw et al. Aug. 6, 1929 1,972,486 Hoover Sept. 4, 1934 2,086,097 Shoemaker July 6, 1937 2,111,657 Benedek Mar. 22, 1938 2,161,917 Forsyth et al June 13, 1939 2,296,348 Hoover May 31, 1939 2,307,849 Mullen Jan. 12, 1943 2,392,364 Caldwell et al. Jan. 8, 1946 2,422,966 I-Ioover June 24, 1947 FOREIGN PATENTS Number Country Date 479,888 Great Britain Feb. 14, 1938 

